Celestia

During these days when
Mars is
closer than it has been in 60,000 years, everyone wants to look skyward for
the red planet.
But for those of us in urban areas a good view may not be possible
(houses, trees, light pollution, and what-not).

Celestia to the rescue!
This space simulator has all the obsessive detail you could want, from the
texture of the Earth, to every moon in the solar system, to distant galaxies.
There are even contributed databases of
ficticious worlds.

On a side note: the desktop icon for Celestia looks an awful lot like the
one for Eclipse, and ended up right
next to it: